Methods for impurity profiling of heroin and cocaine

34

Methods for impurity profiling of heroin and cocaine

Method B7:

Elemental analysis by ICP-MS

Source: R. J. Wells and others, “Trace element analysis of heroin by ICP-MS”,

Chemistry in Australia, vol. 62, No. 7 (1995), p. 14.

Rationale for use: The method measures an abundance of sample trace elements and

is most useful for unadulterated samples. Elemental analysis has been shown to be a

powerful sample-to-sample comparison tool.

Outcome: Aids in the evaluation of samples for case-to-case evidential purposes 

(linkage determinations). Provides additional information required to confirm links

between samples, that is, the method should be used in conjunction with a major com-

ponent analysis.

Method B8:

Abundance of stable isotopes 

15

N and 

13

C 

by Isotope Ratio MS (IRMS)

Sources:  J. R. Ehleringer and others, “Geo-location of heroin and cocaine by stable

isotope ratios”, Forensic Science International, vol. 106, No. 1 (1999), pp. 27-35;

F. Besacier and others, “Isotopic analysis of 

13

C as a tool for comparison and origin

assignment of seized heroin samples”, Journal of Forensic Sciences, vol. 42, No. 3

(1997), pp. 429-434; S. Dautraix and others, “

13

C Isotopic analysis of an acetaminophen

and diacetylmorphine mixture”, Journal of Chromatography A, vol. 756, Nos. 1-2

(1996), pp. 203-210; M. Desage and others, “Gas chromatography with mass spec-

trometry or isotope-ratio mass spectrometry in studying the geographical origin of

heroin”,  Analytica Chimica Acta, vol. 247, No. 2 (1991), pp. 249-254.

Rationale for use: An IRMS method for the measurement of the relative abundance

of stable isotopes 

15

N and 

13

C. The method is designed for unadulterated samples.

Work is ongoing for the application of GC-IRMS to adulterated samples.* 

Outcome: Provides geo-specific information. Aids in the evaluation of samples for

case-to-case evidential purposes (linkage determinations). Provides additional infor-

mation required to confirm links between samples, that is, the method should be used

in conjunction with a major component analysis.

5.

Additional methods

*Personal communication from David Morello, Special Testing and Research Laboratory, Drug

Enforcement Administration, Dulles, Virginia, United States, 2005.

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Methods for impurity profiling

35

C.

Cocaine methods

The reader is referred to chapter III, section A, above for general procedural com-

ments as, for the most part, they apply equally to both heroin and cocaine impu-

rity profiling work. Some useful comments, applicable to both heroin and cocaine,

can also be found in the subsection entitled “Hydrolysis of heroin” in chapter III,

section B, above.

Heroin profiling studies were first initiated during the 1960s and by the mid-

1970s such studies were ongoing in several national laboratories. In contrast, one

of the first works describing a cocaine profiling method was published by Casale

and Waggoner in 1991 [49]. Hence, one might properly expect profiling method-

ologies for cocaine to be significantly less well developed than those for heroin.

However, a relatively small cadre of researchers have taken the art of cocaine

profiling to a level at least on a par with heroin profiling. While the strides made

by those researchers are quite remarkable, they did enjoy some significant advan-

tages. Certainly the 20 or more years of experience gained with heroin profiling

gave them a significant knowledge base from which to start. Additionally, both

the number of and the relative concentration of alkaloidal impurities are frequently

higher in cocaine samples than they are in heroin samples and the cocaine alka-

loidal impurities have not been modified by a synthetic step. 

All of the following cocaine impurity profiling methods can be used for com-

parative analysis work. However, as in the case of heroin profiling, no single

method provides a result specific enough to be used as a stand-alone method for

evidentiary purposes. 

As for heroin, an impurity profile database can be built and subsequently

used for retrospective comparisons. Also similar to heroin, there are consider-

able difficulties attendant with the acquisition of a comprehensive compilation

of current samples of known origin. As a result, it is likely that most laborato-

ries will encounter significant difficulties in establishing regions and/or countries

of origin.

All of the methods described are equally applicable to cocaine base, crack

cocaine and cocaine hydrochloride. However, at the present time it is not possi-

ble to establish links between cocaine base and the cocaine hydrochloride from

which it was prepared. 

As was noted for heroin, those methods which do not include a derivatiza-

tion step prior to GC chromatography all carry a risk of sample component decom-

position during analysis. Scrupulous maintenance of the GC injection port does

minimize that risk; however, benzoic acid measurements will remain very prob-

lematic. Typically, the detection of anhydroecgonine methylester by GC is also

not useful. In nearly all instances this compound is a GC degradation product

(artefact), owing to the decomposition of large tropine alkaloids, principally the

11 truxilline alkaloids. Since the truxilline isomers do not undergo derivatization,

the inclusion of a derivatization step does not provide a viable remedy. 

Annex II, table 4, summarizes many of the major and trace-level alkaloidal

impurities found in cocaine samples. 

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